Tidal tomography of 16 years of orbiter tracking shows a heat anomaly beneath Mars’s southern highlands that may be partially molten and linked to the planet’s crustal differences and past evolution.
Tidal tomography applied to 16 years of orbiter tracking detects a mantle anomaly beneath Mars’s southern hemisphere about 200–400°C hotter than surrounding mantle.
The finding offers a new way to probe Mars’s internal evolution and has implications for crustal dichotomy, magnetization patterns, and past magma production.
The analysis of orbital tracking records reveals a persistent thermal anomaly in the mantle beneath Mars's southern highlands. The anomaly's magnitude—about 200–400°C higher than the surrounding mantle—suggests enhanced heat there. That heat could reduce shear velocity in mantle material and, if high enough, induce partial melting. The anomaly is confined beneath the crust and does not appear to have breached the surface.
Physical context and crustal differences
Mars's southern crust is significantly thicker than the northern crust. That thicker crust can act as a thermal cap, trapping heat in the underlying mantle and slowing any upward migration of melt. The team notes the mantle beneath the northern hemisphere is thinner and comparatively cooler. The warm southern mantle could therefore help explain differences across the planet's crustal dichotomy and regional magnetization patterns if it influenced magmatic and thermal history over time.
Researchers outline two plausible origins supported by the observations. One possibility is that the anomaly is primordial, a long-lived thermal or compositional heterogeneity that has existed since Mars formed and shaped its geodynamic evolution. Another possibility is that a large, ancient impact produced the upwelling or compositional modification that produced the heat anomaly. The current data do not distinguish between these origins.
If the anomaly is partially molten, it signals active or recent magmatic processes at depth that did not reach the surface because of crustal thickness. That pattern could affect crustal thickening and the extent of magnetization in the southern highlands. More broadly, tidal tomography provides a noninvasive tool to map interior structure and can refine thermal models, assess deep-seated magma production, and inform hypotheses about Mars's tectonic and magnetic history.
Follow-up studies are needed to test compositional versus purely thermal explanations for the anomaly, refine its depth and geometry, and search for other anomalies. Continued tidal tomography with ongoing orbiter tracking will improve temporal coverage. Similar radio science and deformation measurements planned for other worlds (for example, Ganymede with ESA's JUICE mission) show the technique's broader applicability to mapping interiors without seismometers.
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